1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a computer program product.
2. Description of the Related Art
A technology for embedding various data in an original image when outputting the original image on a recording medium is widely used in image processings. Examples of data to be embedded into an original image include data on protection of security or contents of the original image, and data for associating the contents of the original image with web pages. Such data is generally embedded as various patterns in an image.
Barcodes are widely known as examples of such patterns. However, barcodes are disadvantageous in that it is necessary to have a space for placing a barcode in the original image, and it is difficult to maintain security of data encoded in the barcode because the barcode may be cut off from the original image. As countermeasures to such situations, conventional technologies for arranging faint background patterns on the original image instead of barcodes are known.
For example, Japanese Patent No. 2833975 discloses dot codes for embedding additional information in an original image. A dot code is formed by a plurality of blocks, each having base points called “marker” in every corner of the block, and dot images indicative of information are arranged inside the block. Furthermore, Japanese Patent No. 3628312 discloses a faint-image embedding apparatus and a faint-image detecting apparatus. The faint-image embedding apparatus can add confidential data in non-text format to a text image. The faint-image detecting apparatus can detect confidential data from a printed document. Moreover, Japanese Patent Application Laid-Open No. 2004-336219 discloses a conventional technology for retrieving embedded data from an original image. In the conventional technology, two-dimensional patterns formed by slash and backslash are embedded as background images in the original image.
However, the conventional technologies are only for embedding data in an image to be output, and not for editing such embedded data (deletion or change of contents of data). For example, while it is required to retrieve data for identifying a printed object that is embedded in an original, it is also required to prevent the data from being retrieved from copies of the original. In this case, the data on the copies needs to be deleted therefrom. Furthermore, when an image is to be copied or printed for a number of times, if identification data of image processing apparatuses that have copied or printed the image can be incrementally embedded in the image, traceability of the image can be realized thereby assuring reliability of the image.